Technical Field
The present disclosure relates to semiconductor fabrication, and more specifically, to a method using a tensile hard mask to minimize buckling in a substrate, and the resulting intermediate semiconductor structure.
Related Art
In integrated circuit devices, groups of openings are formed in semiconductor substrates for use in forming a wide variety of structures such as capacitors, memory, fins, etc. One type of opening that is typically formed in groups in one area of the semiconductor substrate but not in other areas includes deep trenches. Groups of openings can be formed using any conventional process such as patterning a thick oxide mask over the semiconductor substrate, etching the pattern into the substrate in one area, and fully or partially removing the mask. After the openings are formed, the surface topography (or relief) of the area with the openings is typically lower compared to those areas without openings. Subsequent operations have difficulty with the resulting, uneven topography. For example, subsequent alignment and planarizing operations cannot effectively correct for the distortion, leading to variable structure positions and heights. One example structure that has different heights over the openings, e.g., trenches, compared to where no openings are provided include fin-gate structures. The height difference can be, for example, 60-70 nanometers, which is 3-4 times greater than presently acceptable tolerances. Consequently, the varied surface topography severely limits device yield.